The present invention relates to a thermosetting resin composition for providing a cured product which has excellent heat resistance and electric properties and which is useful as a laminated board, encapsulating material, adhesive, coating or electric insulating material.
An epoxy resin is used in various fields since it has excellent heat resistance, adhesion, water resistance, mechanical strength and electric properties. The epoxy resin used is generally a diglycidyl ether of bisphenol A or phenol or cresol novolak type epoxy resin or the like.
However, as the above epoxy resin alone has no flame retardancy, it is often used in conjunction with a halogen-based flame retardant, antimony trioxide or aluminum hydroxide or the like for application in electric and electronic material parts which require high flame retardancy.
However, a halogen-based flame retardant is apprehended as one of the sources of a dioxine which has become a social problem, antimony trioxide has problems such as toxicity and a decrease in insulating properties, and aluminum hydroxide involves such a problem that when it is blended in large quantities, electric properties decrease. Therefore, a flame retardant comprising another compound which can replace these substances or reduce the amounts of these substances is proposed. Or, where flame retarding formulation is strongly desired, there are proposed a method of adding a phosphorus-based compound flame retardant (Japanese Patent Application Laid-open Nos. 11-124489 and 11-166035) and a method of using a compound having a triazine ring (Japanese Laid-open Patent Application Nos. 03-62825 and 08-253557).
However, the addition of a phosphorus-based compound has such a demerit that basic properties such as heat resistance and humidity resistance are lost because a phosphorus-based compound must be used in large quantities to provide sufficient flame retardancy.
The method of using a compound having a triazine ring is advantageous from an environmental point of view because it is a nitrogen compound but has a problem with the effect of improving the flame retardancy of an epoxy cured product because only a small amount of the triazine ring can be introduced into the molecule.
The present invention is to provide a thermosetting resin composition which can provide a cured product having excellent flame retardancy without impairing the heat resistance of an epoxy cured product and contains an epoxy resin and a specific phenol resin curing agent having a triazine ring.
The inventors of the present invention have conducted intensive studies on a compound having a triazine ring and have found that a cured product having an excellent effect of improving flame retardancy can be obtained from a specific phenol resin having at least one triazine ring in the molecule without impairing the performance of an epoxy resin.
Accordingly the present invention relates to:
A thermosetting resin composition comprising the following components (A) and (B):
component (A): an epoxy resin, and
component (B): a phenol resin containing a phenol compound represented by the following general formula (1): 
wherein R1 and R2 are a hydrogen atom or alkyl group having 1 to 4 carbon atoms, R3 is an amino group, alkyl group having 1 to 4 carbon atoms, phenyl group, vinyl group or any one of the following general formula (2) 
and general formula 3: 
[wherein R1 and R2 in the general formulae (2) and (3) are a hydrogen atom or alkyl group having 1 to 4 carbon atoms, and m is an integer of 1 or 2.]
A preferred embodiment of said thermosetting resin composition is that one, wherein the hydroxyl group of the phenol resin as the component (B) is contained in an amount of 0.1 to 2 equivalents based on 1 equivalent of the epoxy group of the epoxy resin as the component (A).
In a more preferred thermosetting resin composition the component (B) is a phenol resin containing a phenol compound represented by the above general formula (1) in an amount of 10 to 90 wt %.
In a further preferred thermosetting resin composition, the component (B) is a phenol resin containing a phenol compound represented by the following general formula(e) (4) and/or (5) 
[wherein R1 and R2 are a hydrogen atom or alkyl group having 1 to 4 carbon atoms, R3 is an amino group, alkyl group having 1 to 4 carbon atoms, phenyl group, vinyl group or any one of the above general formulae (2) and (3), and m is an integer of 1 or 2,] and n is an integer of 0 to 20, in addition to the phenol compound represented by the above general formula (1). 
In a further preferred thermosetting resin compound the component (B) is a phenol resin containing a phenol compound represented by the herein before depicted general formula (4) in an amount of 1 to 45 wt % and/or a phenol resin containing a phenol compound represented by the herein before depicted general formula (5) in an amount of 10 to 80 wt %.
In the most preferred thermosetting resin composition the component (B) is a phenol resin produced by reacting a methylol product of a triazine compound with phenols.
In an other preferred thermosetting resin composition, wherein a curing accelerator is contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the epoxy resin.
In a more preferred thermosetting resin composition, the curing accelerator is a compound selected from the group consisting of tertiary amines, imidazoles and organic phosphines.
Preferred thermosetting resin compositions are comprising a metal hydroxide in an amount of 1 to 50 parts by weight based on 100 parts by weight of the hereinbefore specified epoxy.
More preferablely in the thermosetting resin composition the metal hydroxide is a compound selected from the group consisting of aluminum hydroxide and magnesium hydroxide.
The hereinbefore specified thermosetting resin composition is used for laminated boards, encapsulating materials or powder coatings
Component (A): epoxy resin
The epoxy resin as the component (A) used in the present invention is a general epoxy resin. Examples of the epoxy resin include:
(1) Aromatic Diglycidyl Ethers;
diglycidyl ethers of bisphenol A, diglycidyl ethers of bisphenol F, diglycidyl ethers of 3,3xe2x80x2, 5,5xe2x80x2-tetramethylbisphenol A, diglycidyl ethers of 3,3xe2x80x2, 5,5xe2x80x2-tetramethylbisphenol F, diglycidyl ethers of bisphenol S, diglycidyl ethers of dihydroxyphenyl, diglycidyl ethers of biphenols, diglycidyl ethers of 3,3xe2x80x2, 5,5xe2x80x2-tetramethylbiphenol, diglycidyl ethers of naphthalene diol, etc.
(2) Polyfunctional Epoxies;
phenol novolak type epoxy resins, cresol novolak type epoxy resins, naphthol novolak type epoxy resins, bisphenol A novolak type epoxy resins, epoxy resins obtained from triphenol methane, epoxy resins obtained from tetraphenol ethane, etc.
(3) Others;
glycidyl esters obtained from phthalic acid, hexahydrophthalic acid, dimer acid and the like, glycidylamines obtained from aminophenol, diaminodiphenyl methane and the like, aliphatic epoxies obtained from 1,4-butanediol, 1,6-hexanediol and the like, alicyclic epoxies obtained from cyclohexane dimethanol, hydrogenated bisphenol A and the like, alicyclic aliphatic epoxies obtained from a cycloolefin such as 3,4-epoxycyclohexylmethyl-3xe2x80x2, 4xe2x80x2-epoxycyclohexane carboxylate and peracetic acid, and epoxy resins obtained from a condensation reaction of one or more of the above aromatic diglycidyl ethers, polyfunctional epoxies and others with bisphenols (bisphenol A, bisphenol F, bisphenol S, dihydroxydiphenyl ethers, biphenols, 3,3xe2x80x2, 5,5xe2x80x2-tetramethylbiphenol, naphthalene diol and the like).
Component (B): Phenol Resin
The phenol resin as the component (B) used in the present invention functions as a curing agent for the epoxy resin as the component (A) and contains a phenol compound represented by the following general formula (1), 
having at least one triazine ring in one molecule, [wherein R1 and R2 are a hydrogen atom or alkyl group having 1 to 4 carbon atoms, R3 is an amino group, alkyl group having 1 to 4 carbon atoms, phenyl group, vinyl group or any one of the above general formulas (2) 
and (3): 
[wherein, R1 and R2 are in the general formulae (2) and (3) are a hydrogen atom or alkyl group having 1 to 4 carbon atoms, and m is an integer of 1 or 2. ]
The phenol resin containing a phenol compound represented by the above general formula (1) in an amount of 10 to 90 wt % is preferred.
When the phenol compound represented by the above general formula (1) is contained in the phenol resin in an amount of less than 10 wt %, the heat resistance of an epoxy cured product decreases disadvantageously. When the amount is larger than 90 wt %, the softening temperature of the phenol resin rises, thereby making it difficult to handle the phenol resin, which is not preferable.
The phenol resin containing the phenol compounds represented by the following general formula(4): 
and (5): 
[wherein R1 and R2 are a hydrogen atom or alkyl group having 1 to 4 carbon atoms, R3 is an amino group, alkyl group having 1 to 4 carbon atoms, phenyl group, vinyl group or any one of the above general formulae (2) and (3), and m is an integer of 1 or 2, and n is an integer of 0 to 20, is preferred from the viewpoint of handling properties of the phenol resin.
When the phenol compound represented by the general formula (4) is contained in the phenol resin in an amount of more than 45 wt %, the heat resistance of the epoxy cured product decreases disadvantageously.
The phenol resin containing the phenol compound represented by the general formula (5) in an amount of 10 to 80 wt % is particularly preferred from the viewpoints of handling properties and flame retardancy.
Preferably, the phenol resin of the present invention is first obtained by reacting an aqueous solution of formaldehyde with a triazine ring-containing compound to introduce methylol groups into the triazine ring-containing compound. A large number of triazine rings are introduced into the phenol resin by this reaction, thereby making it possible to improve the flame retardancy of an epoxy cured product.
After a phenol is added to the obtained reaction solution to carry out a dehydration reaction, or the methylol product is alkoxylated with an alcohol to carry out an alcohol removing reaction, unreacted phenol is distilled off to obtain a phenol resin.
The method of carrying out an alcohol removing reaction after the methylol product is alkoxylated with an alcohol is preferred because the homopolymerization of the triazine compound can be prevented.
Examples of the triazine ring-containing compound include melamine, acetoguanamine, ethylguanamine, butylguanamine, benzoguanamine, vinylguanamine and the like.
Examples of the phenol include phenol, cresol, ethylphenol, propylphenol, butylphenol, xylenol, 2-tert-butyl-4-methylphenol, 2-tert-butyl-5-methylphenol, catechol, resorcin and the like.
As for the reaction method, a methylol product is formed by using 1 to 10 moles of formaldehyde based on 1 mole of the triazine ring-containing compound at a temperature of 30 to 150xc2x0 C. The dehydration or alcohol removing reaction is carried out at a temperature of 50 to 200xc2x0 C. by using the phenol in an amount of 2 to 30 moles based on 1 mole of the obtained methylol product to obtain a phenol resin.
The blending ratio of the epoxy resin as the component (A) to the phenol resin as the component (B) is such that the amount of the hydroxyl group of the phenol resin as the component (B) becomes 0.1 to 2 equivalents, preferably 0.15 to 1.5 equivalents based on 1 equivalent of the epoxy group of the epoxy resin as the component (A).
Outside the above range, the heat resistance and the humidity resistance of the epoxy resin curing agent are imbalanced disadvantageously, and therefore not preferable.
A curing accelerator can be added in the thermosetting resin composition of the present invention for the purpose of promoting curing. Preferred examples of the curing accelerator include the following.
(1) Tertiary Amines;
tri-n-butylamine, benzyldimethylamine, 2,4,6-tris(dimethylaminomethyl)phenol, 1,8-diazabicyclo(5,4,0)undecene-7, 1,5-diazabicyclo(4,3,0)nonene-7 and the like, and salts thereof.
(2) Imidazoles;
2-methylimidazole, 2-ethyl-4-methylimidazole, 1-benzyl-2-methylimidazole, 2-undecylimidazole, 2-phenylimidazole and the like, and salts thereof.
(3) Organic Phosphines;
tributylphosphine, tricyclohexylphosphine, triphenylphosphine and tris(dimethoxyphenyl)phosphine, and salts thereof.
These curing accelerators may be used alone or in combination of two or more. The amount of the curing accelerator is 0.01 to 10 parts by weight, preferably 0.02 to 5 parts by weight based on 100 parts by weight of the epoxy resin as the component (A).
When the amount of the curing accelerator is smaller than 0.01 part by weight, the effect of promoting the curing of the composition of the present invention is small and when the amount is larger than 10 parts by weight, the water resistance of a cured product deteriorates disadvantageously, and therefore not preferable.
The flame retardancy can be further improved by containing a metal hydroxide in the thermosetting composition of the present invention.
Examples of the metal hydroxide include aluminum hydroxide, magnesium hydroxide and the like. They may be used in combination of two or more, but aluminum hydroxide is particularly preferred.
The amount of the metal hydroxide is 1 to 50 parts by weight, preferably 2 to 30 parts by weight based on 100 parts by weight of the epoxy resin as the component (A). When the amount of the metal hydroxide is smaller than 1 part by weight, the effect of flame retarding the composition of the present invention is small and when the amount is larger than 50 parts by weight, the electric properties of the cured product deteriorate disadvantageously, and therefore not preferable.
The following components may be added to the thermosetting resin composition of the present invention as required.
(1) Powdery reinforcement and filler; for example, metal oxides such as aluminum oxide and magnesium oxide, metal carbonates such as calcium carbonate and magnesium carbonate, silicon compounds such as diatomaceous earth powder, basic magnesium silicate, burned clay, fine powder silica, molten silica and crystal silica, and others such as kaolin, mica, quartz powder, graphite and molybdenum disulfide, and further, fibrous reinforcement and filler; for example, glass fiber, ceramic fiber, carbon fiber, alumina fiber, silicon carbide fiber, boron fiber, polyester fiber, polyamide fiber and the like.
They are used in an amount of 10 to 900 parts by weight based on 100 parts by weight of the sum of the epoxy resin and the curing agent.
(2) Colorant, pigment and flame retardant such as titanium dioxide, iron black, molybdenum red, iron blue, ultramarine blue, cadmium yellow, cadmium red, antimony trioxide, red phosphorus, bromine compound, triphenyl phosphate and the like.
They are used in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the sum of the epoxy resin and the curing agent.
(3) Curable monomers, oligomers and synthetic resins can be added for the purpose of improving the properties of a resin in the final coating film, adhesive layer, molded product and the like. For example, combination of one or more of an epoxy resin diluent such as monoepoxy, a phenol resin other than the component (B) of the present invention, alkyd resin, melamine resin, fluororesin, vinyl chloride resin, acrylic resin, silicone resin and polyester resin may be used. The proportion of the resin(s) is such that it does not impair the original properties of the resin composition of the present invention, that is, preferably 50 parts or less by weight based on 100 parts by weight of the total of the epoxy resin and the curing agent.
Means of blending the epoxy resin of the present invention, an epoxy resin curing agent and optional components may be thermal melt mixing, melt kneading with a roll or kneader, wet mixing with an appropriate organic solvent, dry mixing, or the like.
Effect of the Invention
The present invention provides an epoxy resin cured product which is cured using a phenol resin having a high flame retardancy unseen conventionally providing effect as a curing agent and whose flame retardancy, heat resistance and humidity resistance are well balanced. Therefore, it can be used for a wide variety of application purposes and advantageously used especially in electric and electronic fields such as semiconductor encapsulating materials, laminated board materials and electric insulating materials.
The following examples and comparative examples are given to further illustrate the present invention, however, without restriction its scope to these embodiments.